Sunday, June 1st, was the start of meteorological summer and it was a busy day in the weather department. Around 1 PM thunderstorms began showing signs of weak rotation and multiple tornado warnings were issued for northern Iowa. Four tornadoes were reported, but why? First we need to understand that these were not your typical tornadoes, these were non-supercell tornadoes sometimes called landspouts. Non-supercell tornadoes are typically not very strong and do not last long, but can still cause damage which is why it is still good practice to shelter in your basement if a warning is issued.
The thunderstorms dropping these non-supercell tornadoes came in contact with boundaries left over by rain which fell Sunday morning. When thunderstorms come in contact with boundaries it can increase their rotation causing the brief spin-ups like we saw Sunday afternoon. This brief tornado shown below was captured just west of Buffalo Center in northern Iowa and lasted only a few minutes courtesy of KLLS radio.
Besides brief, weak tornadoes in northern Iowa other thunderstorms produced small hail. Picture of dime size hail in Glenville.
A shelf cloud was also observed moving through portions of MN/IA prompting severe thunderstorm warnings for eastern Mower County & Fillmore County. Picture below is of a shelf cloud in Osage, IA.
A roll cloud was also observed later Sunday evening as another round of thunderstorms rolled through the area, bringing stronger wind gusts but nothing severe. Picture from Elkton, MN.
Heavy rain was a common occurrence throughout the viewing area with multiple rounds of rain. Austin, MN received over 1” of rain in just 30 minutes causing some minor street flooding.
Storm Tracker Radar Rain Vision estimates that over 3” of rain fell in a few areas.
Because of Sunday’s heavy rains and the possibility for more heavy rain through Monday a flash flood watch has been issued for all of the viewing area through Monday. If you come across a flooded roadway remember to not drive through the water and find a safe route around the flooded street.